Receptacles are referred to as 7-16 receptacles when they have an inside contact diameter of 7 millimeters (mm) and an outside contact diameter of 16 mm. 7-16 receptacles are in widespread use in telecommunications equipment for connecting radiofrequency lines for which there are very severe performance requirements in terms of losses and passive intermodulation.
In general, flanged receptacles are situated as inputs/outputs of duplexer filters, on antennas, and more generally on other pieces of equipment situated between those elements, such as mast amplifiers, lightning arrestors, etc.
To obtain as great as possible a reduction in the intermodulation phenomenon, it is conventional to use receptacles comprising a machined solid body presenting an outside thread and a fastener flange extending perpendicularly to the longitudinal axis of the body, the flange being substantially square in shape with four holes for passing mounting screws.
Those receptacles have the advantage of minimizing junction zones, which are sources of intermodulation, but the drawback of being expensive, heavy and difficult to mount. Mounting conventional receptacles by means of four screws engaged in the corresponding holes of the flange is difficult when it is desired to minimize intermodulation, because it is necessary to obtain a good distribution of pressures in the contact zones.
Proposals also have been made to replace the brass that is conventionally used with an alloy of lighter weight based on zinc (such as zinc alloys sold under the trademark ZAMAK) or aluminum.
The above-described problems remain substantially the same with this configuration, but the parts are less expensive to produce since the tubular bodies can be obtained by molding under pressure. The drawback is such that receptacles are difficult to protect and they are very sensitive to corrosion which requires the conductor to be subjected to surface treatment.
Proposals also have been made to provide 7-16 coaxial receptacles comprising a two-material tubular body, the flange being made of a plastics material that is overmolded or force-fitted on the tubular body that is made of brass.
That solution does not solve the problems associated with final assembly using screws engaged in the holes of the flange.
Furthermore, it is found that large amounts of deformation in use under stress continue because of a relaxation phenomenon that causes contact pressures to decrease over time.